Wi-Fi Calling is the conventional name for a technology that allows cellular packets from your phone to be transferred to your carrier over the internet, and injected back into the cellular network as if they'd been beamed over the air.
Unlike services like Google Hangouts and Skype, which let you talk to other people using call forwarding or an internet-based interface, Wi-Fi Calling lets you use your actual carrier phone number over the internet. Wi-Fi Calling is also distinct from VoIP technology, which lets you use an internet-connected phone exactly as you would a landline. VoIP transfers your voice over the internet to the switched telephone network, whereas Wi-Fi Calling connects your voice to your mobile carrier's network using the internet instead of cell towers.
...which is useful and can save you money...
The system has its advantages in that it can help you conserve plan minutes and texts; calls that happen over Wi-Fi don't count against your plan. Additionally, it can help you make calls using your phone number, even when your network cuts out or you're outside your coverage area. Any basement-dwellers out there?
...if carriers and manufacturers actually adopt it...
At launch, only iPhones on T-Mobile will support Wi-Fi calling. In fact, as of last week all new T-Mobile phones will support the capability, which already comes baked into many Android and Windows Phone handsets. Sprint also supports Wi-Fi Calling for compatible Android phones, but there's no word on any forthcoming support for iPhones.
Wi-Fi Calling is hardly a new idea, but Apple may be forcing everyone's hand by making a big deal about the tech and announcing it before everyone's ready to go. Smaller providers like Republic Wireless have been offering the service for some time, and it shouldn't be surprising that T-Mobile, eager to distinguish itself from others, is the first to jump on board with Apple.
A list of compatible phones on the T-Mobile website gives you a sense for what phones are available with the tech: Everything from the latest flagships, like the Samsung Galaxy S5, to junky or outmoded models like the Samsung Galaxy Avant.
...and if it actually works as promised.
It's worth noting that that despite the hyperbolic claims of Apple SVP Phil Schiller and T-Mobile CEO John Legere, Wi-Fi Calling probably won't be seamless. At least not at the start. While Apple made it sound like you can simply jump from the carrier's spectrum to Wi-Fi and back, the fine print on T-Mobile's own site disclaims confusingly both that "Most devices will not transition between Wi-Fi and the wireless network, " and that "Devices will not transition between Wi-Fi and the cellular network." We've reached out for clarification.
Sprint seems to be in the same pickle. The company's FAQ notes: "A call will disconnect if a caller moves between a Wi-Fi and cellular network."
The key to a seamless handoff may be another technology called Voice over LTE, or VoLTE for short, where your calls already start as packets of data (like Skype) instead of using legacy cellular technology. When everything is just data packets, it shouldn't matter whether they travel along Wi-Fi or cellular networks: they can theoretically take the fastest route to their destination.
Last, AT&T CEO Ralph De la Vega said his company won't implement Wi-Fi Calling until it can offer VoLTE as well for a seamless handoff. And though Republic Wireless claims it's managed a seamless handoff without any LTE whatsoever, it's probably because that carrier is already using a proprietary VoIP app to turn calls into data.
In other words, there's great potential in Wi-Fi Calling, but the technology isn't all the way there yet.
source: gizmodo.com by Mario Aguilar